Before commit
d0f9ca9be1 ("ARM: decompressor: run decompressor in place if loaded via UEFI")
we were rather limited in the choice of base address for the uncompressed
kernel, as we were relying on the logic in the decompressor that blindly
rounds down the decompressor execution address to the next multiple of 128
MiB, and decompresses the kernel there. For this reason, we have a lot of
complicated memory region handling code, to ensure that this memory window
is available, even though it could be occupied by reserved regions or
other allocations that may or may not collide with the uncompressed image.
Today, we simply pass the target address for the decompressed image to the
decompressor directly, and so we can choose a suitable window just by
finding a 16 MiB aligned region, while taking TEXT_OFFSET and the region
for the swapper page tables into account.
So let's get rid of the complicated logic, and instead, use the existing
bottom up allocation routine to allocate a suitable window as low as
possible, and carve out a memory region that has the right properties.
Note that this removes any dependencies on the 'dram_base' argument to
handle_kernel_image(), and so this is removed as well. Given that this
was the only remaining use of dram_base, the code that produces it is
removed entirely as well.
Reviewed-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Tested-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Permit arm32-stub.c to access efi_low_alloc_above() in a subsequent
patch by giving it external linkage and declaring it in efistub.h.
Reviewed-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Tested-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
The way we use the base of DRAM in the EFI stub is problematic as it
is ill defined what the base of DRAM actually means. There are some
restrictions on the placement of FDT and initrd which are defined in
terms of dram_base, but given that the placement of the kernel in
memory is what defines these boundaries (as on ARM, this is where the
linear region starts), it is better to use the image address in these
cases, and disregard dram_base altogether.
Reviewed-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Tested-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Pull Kbuild updates from Masahiro Yamada:
- run the checker (e.g. sparse) after the compiler
- remove unneeded cc-option tests for old compiler flags
- fix tar-pkg to install dtbs
- introduce ccflags-remove-y and asflags-remove-y syntax
- allow to trace functions in sub-directories of lib/
- introduce hostprogs-always-y and userprogs-always-y syntax
- various Makefile cleanups
* tag 'kbuild-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kbuild: stop filtering out $(GCC_PLUGINS_CFLAGS) from cc-option base
kbuild: include scripts/Makefile.* only when relevant CONFIG is enabled
kbuild: introduce hostprogs-always-y and userprogs-always-y
kbuild: sort hostprogs before passing it to ifneq
kbuild: move host .so build rules to scripts/gcc-plugins/Makefile
kbuild: Replace HTTP links with HTTPS ones
kbuild: trace functions in subdirectories of lib/
kbuild: introduce ccflags-remove-y and asflags-remove-y
kbuild: do not export LDFLAGS_vmlinux
kbuild: always create directories of targets
powerpc/boot: add DTB to 'targets'
kbuild: buildtar: add dtbs support
kbuild: remove cc-option test of -ffreestanding
kbuild: remove cc-option test of -fno-stack-protector
Revert "kbuild: Create directory for target DTB"
kbuild: run the checker after the compiler
Pull EFI fixes from Ingo Molnar:
"Various EFI fixes:
- Fix the layering violation in the use of the EFI runtime services
availability mask in users of the 'efivars' abstraction
- Revert build fix for GCC v4.8 which is no longer supported
- Clean up some x86 EFI stub details, some of which are borderline
bugs that copy around garbage into padding fields - let's fix these
out of caution.
- Fix build issues while working on RISC-V support
- Avoid --whole-archive when linking the stub on arm64"
* tag 'efi-urgent-2020-07-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
efi: Revert "efi/x86: Fix build with gcc 4"
efi/efivars: Expose RT service availability via efivars abstraction
efi/libstub: Move the function prototypes to header file
efi/libstub: Fix gcc error around __umoddi3 for 32 bit builds
efi/libstub/arm64: link stub lib.a conditionally
efi/x86: Only copy upto the end of setup_header
efi/x86: Remove unused variables
Pull arm64 fixes from Will Deacon:
"A batch of arm64 fixes.
Although the diffstat is a bit larger than we'd usually have at this
stage, a decent amount of it is the addition of comments describing
our syscall tracing behaviour, and also a sweep across all the modular
arm64 PMU drivers to make them rebust against unloading and unbinding.
There are a couple of minor things kicking around at the moment (CPU
errata and module PLTs for very large modules), but I'm not expecting
any significant changes now for us in 5.8.
- Fix kernel text addresses for relocatable images booting using EFI
and with KASLR disabled so that they match the vmlinux ELF binary.
- Fix unloading and unbinding of PMU driver modules.
- Fix generic mmiowb() when writeX() is called from preemptible
context (reported by the riscv folks).
- Fix ptrace hardware single-step interactions with signal handlers,
system calls and reverse debugging.
- Fix reporting of 64-bit x0 register for 32-bit tasks via
'perf_regs'.
- Add comments describing syscall entry/exit tracing ABI"
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
drivers/perf: Prevent forced unbinding of PMU drivers
asm-generic/mmiowb: Allow mmiowb_set_pending() when preemptible()
arm64: Use test_tsk_thread_flag() for checking TIF_SINGLESTEP
arm64: ptrace: Use NO_SYSCALL instead of -1 in syscall_trace_enter()
arm64: syscall: Expand the comment about ptrace and syscall(-1)
arm64: ptrace: Add a comment describing our syscall entry/exit trap ABI
arm64: compat: Ensure upper 32 bits of x0 are zero on syscall return
arm64: ptrace: Override SPSR.SS when single-stepping is enabled
arm64: ptrace: Consistently use pseudo-singlestep exceptions
drivers/perf: Fix kernel panic when rmmod PMU modules during perf sampling
efi/libstub/arm64: Retain 2MB kernel Image alignment if !KASLR
Since commit 82046702e2 ("efi/libstub/arm64: Replace 'preferred' offset
with alignment check"), loading a relocatable arm64 kernel at a physical
address which is not 2MB aligned and subsequently booting with EFI will
leave the Image in-place, relying on the kernel to relocate itself early
during boot. In conjunction with commit dd4bc60765 ("arm64: warn on
incorrect placement of the kernel by the bootloader"), which enables
CONFIG_RELOCATABLE by default, this effectively means that entering an
arm64 kernel loaded at an alignment smaller than 2MB with EFI (e.g. using
QEMU) will result in silent relocation at runtime.
Unfortunately, this has a subtle but confusing affect for developers
trying to inspect the PC value during a crash and comparing it to the
symbol addresses in vmlinux using tools such as 'nm' or 'addr2line';
all text addresses will be displaced by a sub-2MB offset, resulting in
the wrong symbol being identified in many cases. Passing "nokaslr" on
the command line or disabling "CONFIG_RANDOMIZE_BASE" does not help,
since the EFI stub only copies the kernel Image to a 2MB boundary if it
is not relocatable.
Adjust the EFI stub for arm64 so that the minimum Image alignment is 2MB
unless KASLR is in use.
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: David Brazdil <dbrazdil@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This reverts commit 5435f73d5c, which is no longer needed now
that the minimum GCC version has been bumped to v4.9
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
The prototype of the functions handle_kernel_image & efi_enter_kernel
are defined in efi-stub.c which may result in a compiler warnings if
-Wmissing-prototypes is set in gcc compiler.
Move the prototype to efistub.h to make the compiler happy.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Link: https://lore.kernel.org/r/20200706172609.25965-2-atish.patra@wdc.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Some Makefiles already pass -ffreestanding unconditionally.
For example, arch/arm64/lib/Makefile, arch/x86/purgatory/Makefile.
No problem report so far about hard-coding this option. So, we can
assume all supported compilers know -ffreestanding.
I confirmed GCC 4.8 and Clang manuals document this option.
Get rid of cc-option from -ffreestanding.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Some Makefiles already pass -fno-stack-protector unconditionally.
For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile.
No problem report so far about hard-coding this option. So, we can
assume all supported compilers know -fno-stack-protector.
GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN)
Get rid of cc-option from -fno-stack-protector.
Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which is always 'y'.
Note:
arch/mips/vdso/Makefile adds -fno-stack-protector twice, first
unconditionally, and second conditionally. I removed the second one.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
When copying the setup_header into the boot_params buffer, only the data
that is actually part of the setup_header should be copied.
efi_pe_entry() currently copies the entire second sector, which
initializes some of the fields in boot_params beyond the setup_header
with garbage (i.e. part of the real-mode boot code gets copied into
those fields).
This does not cause any issues currently because the fields that are
overwritten are padding, BIOS EDD information that won't get used, and
the E820 table which will get properly filled in later.
Fix this to only copy data that is actually part of the setup_header
structure.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Commit
987053a300 ("efi/x86: Move command-line initrd loading to efi_main")
made the ramdisk_addr/ramdisk_size variables in efi_pe_entry unused, but
neglected to delete them.
Delete these unused variables.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
On 32-bit ARM, we may boot at HYP mode, or with the MMU and caches off
(or both), even though the EFI spec does not actually support this.
While booting at HYP mode is something we might tolerate, fiddling
with the caches is a more serious issue, as disabling the caches is
tricky to do safely from C code, and running without the Dcache makes
it impossible to support unaligned memory accesses, which is another
explicit requirement imposed by the EFI spec.
So take note of the CPU mode and MMU state in the EFI stub diagnostic
output so that we can easily diagnose any issues that may arise from
this. E.g.,
EFI stub: Entering in SVC mode with MMU enabled
Also, capture the CPSR and SCTLR system register values at EFI stub
entry, and after ExitBootServices() returns, and check whether the
MMU and Dcache were disabled at any point. If this is the case, a
diagnostic message like the following will be emitted:
efi: [Firmware Bug]: EFI stub was entered with MMU and Dcache disabled, please fix your firmware!
efi: CPSR at EFI stub entry : 0x600001d3
efi: SCTLR at EFI stub entry : 0x00c51838
efi: CPSR after ExitBootServices() : 0x600001d3
efi: SCTLR after ExitBootServices(): 0x00c50838
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>
Commit 9302c1bb8e ("efi/libstub: Rewrite file I/O routine") introduced a
regression that made a couple of (badly configured) systems fail to
boot [1]: Until 5.6, we silently accepted Unix-style file separators in
EFI paths, which might violate the EFI standard, but are an easy to make
mistake. This fix restores the pre-5.7 behaviour.
[1] https://bbs.archlinux.org/viewtopic.php?id=256273
Fixes: 9302c1bb8e ("efi/libstub: Rewrite file I/O routine")
Signed-off-by: Philipp Fent <fent@in.tum.de>
Link: https://lore.kernel.org/r/20200615115109.7823-1-fent@in.tum.de
[ardb: rewrite as chained if/else statements]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Commit
bbf8e8b0fe ("efi/libstub: Optimize for size instead of speed")
changed the optimization level for the EFI stub to -Os from -O2.
Andrey Ignatov reports that this breaks the build with gcc 4.8.5.
Testing on godbolt.org, the combination of -Os,
-fno-asynchronous-unwind-tables, and ms_abi functions doesn't work,
failing with the error:
sorry, unimplemented: ms_abi attribute requires
-maccumulate-outgoing-args or subtarget optimization implying it
This does appear to work with gcc 4.9 onwards.
Add -maccumulate-outgoing-args explicitly to unbreak the build with
pre-4.9 versions of gcc.
Reported-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200605150638.1011637-1-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Merge the state of the locking kcsan branch before the read/write_once()
and the atomics modifications got merged.
Squash the fallout of the rebase on top of the read/write once and atomic
fallback work into the merge. The history of the original branch is
preserved in tag locking-kcsan-2020-06-02.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Pull ARM updates from Russell King:
- remove a now unnecessary usage of the KERNEL_DS for
sys_oabi_epoll_ctl()
- update my email address in a number of drivers
- decompressor EFI updates from Ard Biesheuvel
- module unwind section handling updates
- sparsemem Kconfig cleanups
- make act_mm macro respect THREAD_SIZE
* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm:
ARM: 8980/1: Allow either FLATMEM or SPARSEMEM on the multiplatform build
ARM: 8979/1: Remove redundant ARCH_SPARSEMEM_DEFAULT setting
ARM: 8978/1: mm: make act_mm() respect THREAD_SIZE
ARM: decompressor: run decompressor in place if loaded via UEFI
ARM: decompressor: move GOT into .data for EFI enabled builds
ARM: decompressor: defer loading of the contents of the LC0 structure
ARM: decompressor: split off _edata and stack base into separate object
ARM: decompressor: move headroom variable out of LC0
ARM: 8976/1: module: allow arch overrides for .init section names
ARM: 8975/1: module: fix handling of unwind init sections
ARM: 8974/1: use SPARSMEM_STATIC when SPARSEMEM is enabled
ARM: 8971/1: replace the sole use of a symbol with its definition
ARM: 8969/1: decompressor: simplify libfdt builds
Update rmk's email address in various drivers
ARM: compat: remove KERNEL_DS usage in sys_oabi_epoll_ctl()
Pull arm64 updates from Will Deacon:
"A sizeable pile of arm64 updates for 5.8.
Summary below, but the big two features are support for Branch Target
Identification and Clang's Shadow Call stack. The latter is currently
arm64-only, but the high-level parts are all in core code so it could
easily be adopted by other architectures pending toolchain support
Branch Target Identification (BTI):
- Support for ARMv8.5-BTI in both user- and kernel-space. This allows
branch targets to limit the types of branch from which they can be
called and additionally prevents branching to arbitrary code,
although kernel support requires a very recent toolchain.
- Function annotation via SYM_FUNC_START() so that assembly functions
are wrapped with the relevant "landing pad" instructions.
- BPF and vDSO updates to use the new instructions.
- Addition of a new HWCAP and exposure of BTI capability to userspace
via ID register emulation, along with ELF loader support for the
BTI feature in .note.gnu.property.
- Non-critical fixes to CFI unwind annotations in the sigreturn
trampoline.
Shadow Call Stack (SCS):
- Support for Clang's Shadow Call Stack feature, which reserves
platform register x18 to point at a separate stack for each task
that holds only return addresses. This protects function return
control flow from buffer overruns on the main stack.
- Save/restore of x18 across problematic boundaries (user-mode,
hypervisor, EFI, suspend, etc).
- Core support for SCS, should other architectures want to use it
too.
- SCS overflow checking on context-switch as part of the existing
stack limit check if CONFIG_SCHED_STACK_END_CHECK=y.
CPU feature detection:
- Removed numerous "SANITY CHECK" errors when running on a system
with mismatched AArch32 support at EL1. This is primarily a concern
for KVM, which disabled support for 32-bit guests on such a system.
- Addition of new ID registers and fields as the architecture has
been extended.
Perf and PMU drivers:
- Minor fixes and cleanups to system PMU drivers.
Hardware errata:
- Unify KVM workarounds for VHE and nVHE configurations.
- Sort vendor errata entries in Kconfig.
Secure Monitor Call Calling Convention (SMCCC):
- Update to the latest specification from Arm (v1.2).
- Allow PSCI code to query the SMCCC version.
Software Delegated Exception Interface (SDEI):
- Unexport a bunch of unused symbols.
- Minor fixes to handling of firmware data.
Pointer authentication:
- Add support for dumping the kernel PAC mask in vmcoreinfo so that
the stack can be unwound by tools such as kdump.
- Simplification of key initialisation during CPU bringup.
BPF backend:
- Improve immediate generation for logical and add/sub instructions.
vDSO:
- Minor fixes to the linker flags for consistency with other
architectures and support for LLVM's unwinder.
- Clean up logic to initialise and map the vDSO into userspace.
ACPI:
- Work around for an ambiguity in the IORT specification relating to
the "num_ids" field.
- Support _DMA method for all named components rather than only PCIe
root complexes.
- Minor other IORT-related fixes.
Miscellaneous:
- Initialise debug traps early for KGDB and fix KDB cacheflushing
deadlock.
- Minor tweaks to early boot state (documentation update, set
TEXT_OFFSET to 0x0, increase alignment of PE/COFF sections).
- Refactoring and cleanup"
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (148 commits)
KVM: arm64: Move __load_guest_stage2 to kvm_mmu.h
KVM: arm64: Check advertised Stage-2 page size capability
arm64/cpufeature: Add get_arm64_ftr_reg_nowarn()
ACPI/IORT: Remove the unused __get_pci_rid()
arm64/cpuinfo: Add ID_MMFR4_EL1 into the cpuinfo_arm64 context
arm64/cpufeature: Add remaining feature bits in ID_AA64PFR1 register
arm64/cpufeature: Add remaining feature bits in ID_AA64PFR0 register
arm64/cpufeature: Add remaining feature bits in ID_AA64ISAR0 register
arm64/cpufeature: Add remaining feature bits in ID_MMFR4 register
arm64/cpufeature: Add remaining feature bits in ID_PFR0 register
arm64/cpufeature: Introduce ID_MMFR5 CPU register
arm64/cpufeature: Introduce ID_DFR1 CPU register
arm64/cpufeature: Introduce ID_PFR2 CPU register
arm64/cpufeature: Make doublelock a signed feature in ID_AA64DFR0
arm64/cpufeature: Drop TraceFilt feature exposure from ID_DFR0 register
arm64/cpufeature: Add explicit ftr_id_isar0[] for ID_ISAR0 register
arm64: mm: Add asid_gen_match() helper
firmware: smccc: Fix missing prototype warning for arm_smccc_version_init
arm64: vdso: Fix CFI directives in sigreturn trampoline
arm64: vdso: Don't prefix sigreturn trampoline with a BTI C instruction
...
Commit
987053a300 ("efi/x86: Move command-line initrd loading to efi_main")
moved the command-line initrd loading into efi_main(), with a check
to ensure that it was attempted only if the EFI stub was booted via
efi_pe_entry rather than the EFI handover entry.
However, in the case where it was booted via handover entry, and thus an
initrd may have already been loaded by the bootloader, it then wrote 0
for the initrd address and size, removing any existing initrd.
Fix this by checking if size is positive before setting the fields in
the bootparams structure.
Fixes: 987053a300 ("efi/x86: Move command-line initrd loading to efi_main")
Reported-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lkml.kernel.org/r/20200527232602.21596-1-nivedita@alum.mit.edu
More EFI changes for v5.8:
- Rename pr_efi/pr_efi_err to efi_info/efi_err, and use them consistently
- Simplify and unify initrd loading
- Parse the builtin command line on x86 (if provided)
- Implement printk() support, including support for wide character strings
- Some fixes for issues introduced by the first batch of v5.8 changes
- Fix a missing prototypes warning
- Simplify GDT handling in early mixed mode thunking code
- Some other minor fixes and cleanups
Conflicts:
drivers/firmware/efi/libstub/efistub.h
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fix a missing prototype warning by adding a forward declaration
for the PE/COFF entrypoint, and while at it, align the function
name between the x86 and ARM versions of the stub.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Now that we removed the memory limit for the allocation of the
command line, there is no longer a need to use the page based
allocator so switch to a pool allocation instead.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Now we can use snprintf to do the UTF-16 to UTF-8 translation for the
command line.
Drop the special "zero" trick to handle an empty command line. This was
unnecessary even before this since with options_chars == 0,
efi_utf16_to_utf8 would not have accessed options at all. snprintf won't
access it either with a precision of 0.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-25-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
efi_convert_cmdline currently overestimates the length of the equivalent
UTF-8 encoding.
snprintf can now be used to do the conversion to UTF-8, however, it does
not have a way to specify the size of the UTF-16 string, only the size
of the resulting UTF-8 string. So in order to use it, we need to
precalculate the exact UTF-8 size.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-24-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Use the efi_printk function in efi_info/efi_err, and add efi_debug. This
allows formatted output at different log levels.
Add the notion of a loglevel instead of just quiet/not-quiet, and
parse the efi=debug kernel parameter in addition to quiet.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200520170223.GA3333632@rani.riverdale.lan/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
The decompressor can load from anywhere in memory, and the only reason
the EFI stub code relocates it is to ensure it appears within the first
128 MiB of memory, so that the uncompressed kernel ends up at the right
offset in memory.
We can short circuit this, and simply jump into the decompressor startup
code at the point where it knows where the base of memory lives. This
also means there is no need to disable the MMU and caches, create new
page tables and re-enable them.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
If we get an invalid conversion specifier, bail out instead of trying to
fix it up. The format string likely has a typo or assumed we support
something that we don't, in either case the remaining arguments won't
match up with the remaining format string.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-16-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Consolidate the actual output of the formatted text into one place.
Fix a couple of edge cases:
1. If 0 is printed with a precision of 0, the printf specification says
that nothing should be output, with one exception (2b).
2. The specification for octal alternate format (%#o) adds the leading
zero not as a prefix as the 0x for hexadecimal is, but by increasing
the precision if necessary to add the zero. This means that
a. %#.2o turns 8 into "010", but 1 into "01" rather than "001".
b. %#.o prints 0 as "0" rather than "", unlike the situation for
decimal, hexadecimal and regular octal format, which all output an
empty string.
Reduce the space allocated for printing a number to the maximum actually
required (22 bytes for a 64-bit number in octal), instead of the 66
bytes previously allocated.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-15-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
